SEGA Genesis Development

SEGA Genesis

The SEGA Genesis (US) / Mega Drive (everywhere else) was a 1988 game console, known for great arcade ports, FM sound, and impressive 2D graphics. It had a Motorola 68000 CPU, 64 KB main RAM, and 64 KB Video RAM. One of the most well-known games for the system is Sonic the Hedgehog, developed by SEGA and released in 1991. This page contains a series of articles about this hardware, including how to program for it, starting from the very basics.

Some of these articles have accompanying example code, available on GitHub.

MC68000/Genesis References:

• M68000 Assembler Reference Manual - Explains assembler directives
• Motorola 68000 Reference Manual - Motorola 68000 Reference Manual
• MegaDrive Development Wiki - Genesis programming references
• Flint/DARKNESS: MC 680x0 Reference 1.1 - Has detailed 68000 info, including Instruction timing, also mirrored on neogeodev.org
• Plutiedev guides - Very useful Genesis game development articles
• SEGA Retro: Mega Drive Technical Information - Genesis Technical Information
• SEGA Retro: Sega Mega Drive - General information about the Genesis

Tutorials:

• MarkeyJester's MC68k Beginner's Tutorial - Great MC68000 tutorial
• Marc's Realm - SEGA MegaDrive programming info
• Big Evil Corporation - SEGA MegaDrive programming info by Matt Phillips

Tools:

• vasm - Open source multi-CPU assembler

Emulators:

• mednafen - Great multi-system emulator
• Exodus - Modular emulator with a lot of debugging functionality
• MAME - Multi-system emulator, emulates thousands of systems
• Regen - Genesis emulator, with great graphics debugging functionality
• BlastEm - Accurate Genesis emulator

Hardware:

• MiSTer FPGA - Very accurate FPGA-based hardware emulation
• krikzz.com: Mega EverDrive X5 - Genesis/MD cartridge that allows running any ROM.

SEGA Genesis: Building a ROM
Getting started with SEGA Genesis development, and building a ROM that will run on an emulator and on a real Genesis.

• originally posted 2017-06-11
• updated 2022-10-12

Genesis hardware

SEGA Genesis: Debugging
2022-07-29
Debugging your SEGA Genesis ROMs, including a new way of adding symbols in the MAME debugger using VASM.

CRASH!

SEGA Genesis: Characters and Playfields
2017-08-06
A description of the basic building blocks of Genesis graphics, and how they are put together to form screen images. 8x8 16-color tiles are mapped to form playfields. A couple of games are analyzed, including some more advanced techniques, usable for rendering polygons.

Tile graphics (Zombies Ate My Neighbours)

SEGA Genesis: Video Display Processor
2017-08-01
A SEGA Genesis graphics tutorial, that explains how to access the 'Video Display Processor' (VDP) graphics processor.

Contra: Hard Corps

SEGA Genesis: Printing Text
2017-09-10
Building on the previous entry, it is explained how the VDP can be used to output text to the screen. This includes creating a font, loading it to graphics memory, writing character indices to playfields, and wrapping it into a useful subroutine.

Text output

SEGA Genesis: Scrolling
2017-07-27
The different scroll modes of the Genesis are covered, as well as code for simple full screen smooth scrolling.

Thunderforce 4

SEGA Genesis: Code Structure
2018-07-16
A few examples of assembly code structure is explored, including variables, arrays and structures, function calling conventions, and how to implement the State Pattern.

Menu

SEGA Genesis: Initialization
2018-07-01
A detailed look at a complete initialization.

Contra: Hard Corps ROM chip

SEGA Genesis: Framebuffer Rendering
2022-07-31
Is framebuffer rendering possible on the Genesis?

Framebuffer rendering with color cycling

SEGA Genesis: Mandelbrot
2022-07-29
Mandelbrot example.

Mandelbrot set on the Genesis